Geophysics and Geophysical Exploration ISSN:1229-1064(Print) 2384-051X(Online) 지구물리와 물리탐사

To reveal and classify site characteristics in densely populated areas in Chuncheon, Korea, Rayleigh-waves wererecorded at 50 sites including four sites in the forest area using four 1-Hz velocity sensors and 24 4.5-Hz verticalgeophones during the period of January 2011 to May 2013. Dispersion curves of the Rayleigh waves obtained by theextended spatial autocorrelation method were inverted to derive shear-wave velocity (vs) models comprising 40 horizontallayers of 1-m thickness. Depths to weathered rocks (Db), shear wave velocities of these basement rocks ( ), averagevelocities of the overburden layer ( ), and the average velocity to a depth of 30 m (vs30), were then derived fromthose models. The estimated values of Db, , , and vs30 for 46 sites at lower altitudes were in the ranges of 5 to29 m, 404 to 561 m/s, 208 to 375 ms/s, and 226 to 583 m/s, respectively. According to the Korean building code forseismic design, the estimated vs30 indicates that the lower altitude areas in Chuncheon are classified as SC (very densesoil and soft rock) or SD (stiff soil). To determine adequate proxies for vs30, we compared the computed values withland cover, lithology, topographic slope, and surface elevation at each of the measurement sites. Due to a weak correlation(r = 0.41) between vs30 and elevation, the best proxy of them, applications of this proxy to Chuncheon of a relativelysmall area seem to be limited.